Dry process formation of solid state lithium ion cell

ABSTRACT

Methods for preparing an electrode may include compressing an electrode dry mixture comprising an active material and an electrolyte material to form an electrode film. An electrolyte dry mixture or a stand-alone solid-state electrolyte film is compressed against a surface of the electrode film to form a laminate of an electrolyte layer and the electrode film. The electrolyte dry mixture may include the electrolyte material. Compressing the electrode dry mixture may include calendering the electrode dry mixture. Compressing the electrolyte dry mixture or stand-alone electrolyte film may be accomplished also by calendering. The electrolyte material may include a glass ceramic and, optionally, an air-stabilizing dopant. The glass ceramic may include Li 3 PS 4 . Thus, the electrodes may include a composite cathode and a solid-state electrolyte layer. The methods may be applicable for a solvent-free process to form electrodes and electrochemical cells and batteries including the electrodes.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of priority under 35 U.S.C. § 119(e)to U.S. Provisional Application Ser. No. 62/626,923, filed Feb. 6, 2018,incorporated herein by reference in its entirety.

STATEMENT OF GOVERNMENT RIGHTS

This disclosure was created with Government support under Contract No.W911QX-17-P-0175 awarded by the United States Army. The Government hascertain rights in this invention.

FIELD

This disclosure relates to batteries and to methods for formingbatteries and components thereof. More specifically, the disclosurerelates to electrodes, separators, and electrolytes suitable for use insolid state lithium ion or sodium ion batteries, and to methods forforming batteries including the same.

BACKGROUND

Rechargeable lithium-ion batteries are used increasingly in essentialapplications such as powering electric/hybrid vehicles, cellulartelephones, and cameras. Recharging these battery systems is achievedusing electrical energy to reverse the chemical reaction between and atthe electrodes used to power the device during battery discharge therebypriming the battery to be capable of delivering additional electricalpower.

Solid electrolyte systems are believed to provide significant safetyadvantages due to the reduction of the possibility of thermal runawaythat is more likely to occur in the presence of liquid electrolytes usedin conventional lithium ion batteries. The primary challenges facingsolid state electrolytes in practice, however, are low conductivity,limited stability and poor mechanical properties. New solid stateelectrolytes (SSE) are emerging with suitable intrinsic conductivity forlithium ion battery architecture but still face key technical challengesby stability and the availability of scalable processes to produce themwith the necessary combination of thickness, uniformity, interfacialimpedance and mechanical strength.

Whether as glass or in ceramic form, solid state ionic conductors foruse in solid state batteries generally require high temperaturesintering or vapor deposition to consolidate the films and manageinterfacial impedance. The resulting films are brittle, and availableconsolidation processes have limited production to low capacity devicesor small disks.

Accordingly, ongoing needs exist for materials and methods that improveproperties of electrochemical cells including solid state electrolytesand that increase processibility within fabrication steps for theelectrochemical cells.

SUMMARY

Some embodiments of this disclosure are directed to methods forpreparing an electrode. The methods include compressing an electrode drymixture to form an electrode film of an electrode material, theelectrode dry mixture comprising an active material and an electrolytematerial. In some embodiments, the methods may further includecompressing an electrolyte dry mixture against a surface of theelectrode film to form an electrolyte layer on the surface of theelectrode film, the electrolyte dry mixture comprising the electrolytematerial. In other embodiments, the methods may further includecompressing an electrolyte dry mixture to form a stand-alone solid-stateelectrolyte film, the electrolyte dry mixture comprising the electrolytematerial, then compressing the stand-alone solid-state electrolyte filmagainst a surface of the electrode film to form a laminate of theelectrode film and the solid-state electrolyte film. In someembodiments, compressing the electrode dry mixture may includecalendering the electrode dry mixture; and compressing the electrolytedry mixture may include applying the electrolyte dry mixture to thesurface of the electrode film and then calendering the electrolyte drymixture against the surface of the electrode film. In some embodiments,the electrolyte material may include a glass ceramic and, optionally, anair-stabilizing dopant.

Further embodiments are directed to electrodes prepared by the methodsdescribed in this disclosure.

Still further embodiments are directed to stand-alone solid-stateelectrolyte films prepared by compressing or calendering an electrolytedry mixture comprising an electrolyte mixture such as Li₃PS₄ glassceramic and an optional binder, for example.

Still further embodiments are directed to electrochemical cells orbatteries including at least one electrode prepared by the methodsdescribed in this disclosure.

Additional features and advantages of the embodiments described hereinwill be set forth in the detailed description which follows, and in partwill be readily apparent to those skilled in the art from thatdescription or recognized by practicing the embodiments describedherein, including the detailed description which follows, the claims, aswell as the appended drawings.

It is to be understood that both the foregoing general description andthe following detailed description describe various embodiments and areintended to provide an overview or framework for understanding thenature and character of the claimed subject matter. The accompanyingdrawings are included to provide a further understanding of the variousembodiments, and are incorporated into and constitute a part of thisspecification. The drawings illustrate the various embodiments describedherein, and together with the description serve to explain theprinciples and operations of the claimed subject matter.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-section of an example solid-state electrode preparedby methods according to embodiments of this disclosure.

FIG. 2 is a cross-section of an example electrochemical cell including asolid-state electrode prepared by methods according to embodiments ofthis disclosure.

FIG. 3 is a cross-section of an example battery stack including asolid-state electrode prepared by methods according to embodiments ofthis disclosure.

FIG. 4 is a cross-section of an example protected-anode battery stackincluding a solid-state electrode prepared by methods according toembodiments of this disclosure.

FIGS. 5A and 5B are a schematic of an example method for forming asolid-state electrode according to embodiments of this disclosure.

FIG. 6 is a schematic process to form a composite cathode filmincorporated with solid-state electrolyte.

FIG. 7 is a schematic of a lamination process for forming a multilayerbattery stack including an anode, current collectors, and solid-stateelectrodes according to embodiments.

FIG. 8 is a schematic of a process for preparing an electrochemical cellincluding a solid-state electrode and an anode having an anodeprotective layer.

FIG. 9 is a schematic of an additional process for preparing anelectrochemical cell including a solid-state electrode and an anodehaving an anode protective layer.

FIG. 10 is a stacked x-ray diffractogram of lithium phosphorus sulfide75Li₂S·25P₂S₅ (LPS) solid electrolytes in a glass state before annealingand a glass ceramic state after annealing.

FIG. 11 is a Raman spectrum of the LPS solid electrolyte.

FIG. 12 is a side-by-side impedance plot comparing LPS in glass stateand LPS in glass-ceramic state.

FIG. 13 is a cyclic voltammogram of a Pt/LPS/Li cell from −0.5 V to +5 Vat a scan rate of 0.1 mV/s.

FIG. 14 is a graph of discharge rate capability for an electrochemicalcell including a lithium cobalt oxide (LCO) cathode, an LPS sold-stateelectrolyte, and a Li anode. The cell was charged at C/10 rate anddischarged at various rates (i.e., C/10, C/5, and C/2). The cut-offvoltage was 4.2 V to 2.7 V.

FIG. 15 is a graph of capacity and efficiency over number of cycles fora LCO/LPS/Li electrochemical cell.

FIG. 16 is a graph of cycle life for a LCO/LPS/Li electrochemical cellat 2.7 V to 4.2 V and C/5.

FIG. 17 is a charge and discharge voltage profile of two LCO cathodesfrom 2.7 V to 4.2 V at C/10.

FIG. 18 is a graph of Li⁺ ionic conductivity over time of LPS materialdoped with ZnO and exposed to air.

DETAILED DESCRIPTION

The following description of particular aspect(s) is merely exemplary innature and is in no way intended to limit the scope of the disclosure,its application, or uses, which may, of course, vary. The materials andprocesses are described with relation to the non-limiting definitionsand terminology included herein. These definitions and terminology arenot designed to function as a limitation on the scope or practice of thedisclosure, but are presented for illustrative and descriptive purposesonly. While the processes or compositions are described as an order ofindividual steps or using specific materials, it is appreciated thatsteps or materials may be interchangeable such that the description ofthe disclosure may include multiple parts or steps arranged in many waysas is readily appreciated by one of skill in the art.

It will be understood that, although the terms “first,” “second,”“third,” etc. may be used herein to describe various elements,components, regions, layers, and/or sections, these elements,components, regions, layers, and/or sections should not be limited bythese terms. These terms are only used to distinguish one element,component, region, layer, or section from another element, component,region, layer, or section. Thus, “a first ‘element’”, “component,”“region,” “layer,” or “section” discussed below could be termed a second(or other) element, component, region, layer, or section withoutdeparting from the teachings herein.

The terminology used herein is for the purpose of describing particularaspects of the disclosure only and is not intended to be limiting. Asused herein, the singular forms “a,” “an,” and “the” are intended toinclude the plural forms, including “at least one,” unless the contextclearly indicates otherwise. Unless indicated otherwise, the term “or”is equivalent to “and/or.” As used herein, the term “and/or” includesany and all combinations of one or more of the associated listed items.It will be further understood that the terms “comprises” and/or“comprising,” or “includes” and/or “including” when used in thisspecification, specify the presence of stated features, regions,integers, steps, operations, elements, and/or components, but do notpreclude the presence or addition of one or more other features,regions, integers, steps, operations, elements, components, and/orgroups thereof. The term “or a combination thereof” means a combinationincluding at least one of the foregoing elements.

Unless otherwise defined, all terms (including technical and scientificterms) used herein have the same meaning as commonly understood by oneof ordinary skill in the art to which this disclosure belongs. It shouldbe further understood that terms such as those defined in commonly useddictionaries, should be interpreted as having a meaning that isconsistent with their meaning in the context of the relevant art and thepresent disclosure, and will not be interpreted in an idealized oroverly formal sense unless expressly so defined herein.

As used herein, “absorbing” can mean: intercalation or insertion orconversion alloying reactions of lithium with the active materials.

As used herein, “desorbing” can mean: de-intercalation or de-insertionor conversion de-alloying reactions of lithium with the activematerials.

As used herein, in the context of the Li-ion cell, “cathode” meanspositive electrode and “anode” means the negative electrode.

As used herein an “active material” is a material that participates inelectrochemical charge/discharge reaction of an electrochemical cellsuch as by absorbing or desorbing lithium.

As used herein, “fibrillizable” can mean capable of processing into theformation of fibrils.

As used herein, “intermixing” can mean forming a mixture by mixing amass of ingredients. Intermixing can mean high-shear mixing to effectfibrillization.

As used herein, “mechanical strength” can mean the ability of a materialto withstand an applied load without failure or deformation.

As used herein, “surface roughness” can mean the roughness or a surfacetexture defined by deviations in the normal vector of a real surfacefrom its ideal form. Surface roughness may include complex shapes madeof a series of peaks and troughs/pores of varying heights, depths, andspacing.

Embodiments of this disclosure include electrodes including a solidstate electrolyte (SSE). Further embodiments of this disclosure includeelectrochemical cells, for example solid state batteries (SSB), thatinclude an electrode having a SSE. In some embodiments, the electrodehaving the SSE may be prepared by solvent-free electrode fabrication.

Limited conductivity dictates that solid electrolytes be incorporatedinto cells as thin films. Production routes starting from vapordeposition, such as used previously, are not economical. Priorproduction routes starting from powders generally entail sintering orother consolidation processes that are limited by poor mechanicalstrength, thermal expansion mismatch, non-flexibility, or uniformitylimitations. Improvement is also needed in raw material costs andcompatibility with unit operations suitable for high-volume production.

Example configurations for solid-state electrodes, electrochemical cellsincluding the solid-state electrodes, and solid-state batteries will nowbe described. Methods for preparing the electrodes will be describedsubsequently.

Referring to FIG. 1 , a solid-state electrode 1 includes a cathode 2 anda solid-state electrolyte 3. These components will be describedsubsequently in greater detail.

Referring to FIG. 2 , an electrochemical cell 10 includes a solid-stateelectrode 1, an anode 20, optionally an anode current collector 30,optionally a cathode current collector 40, and optionally an anodeprotective layer 50. The solid-state electrode 1 includes a cathode 2and a solid-state electrolyte 3. These components will be describedsubsequently in greater detail.

Referring to FIG. 3 , a solid-state battery 100 in one exampleconfiguration includes a multicell battery stack 110 of nelectrochemical cells and an end cathode current collector 60, where nmay be equal to 1, from 1 to 2, from 1 to 10, from 1 to 50, from 1 to100, from 1 to 1000, from 1 to 10,000, or from 1 to greater than 10,000.Each repeating unit of the multicell battery stack 110 may include afirst solid-state electrode 1 a having a first cathode 2 a and a firstsolid-state electrolyte 3 a. The first solid-state electrode 1 a isoriented such that: the first cathode 2 a is between the firstsolid-state electrolyte 3 a and a cathode current collector 40, and thefirst solid-state electrolyte 3 a is between the first cathode 2 a and afirst anode 20 a. Each repeating unit of the multicell battery stack 110may further include a second solid-state electrode 1 b having a secondcathode 2 b and a second solid-state electrolyte 3 b. The secondsolid-state electrode 1 b is oriented such that: the second cathode 2 bis between the second solid-state electrolyte 3 b and a cathode currentcollector of an adjoining cell (not shown) or the end cathode currentcollector 60, and the second solid-state electrolyte 3 b is between thesecond cathode 2 b and a second anode 20 b. Each repeating unit of themulticell battery stack 110 may include an anode current collector 30between the first anode 20 a and the second anode 20 b. These componentswill be described subsequently in greater detail.

Referring to FIG. 4 , an protected-anode solid-state battery 101 in oneexample configuration includes a protected-anode multicell battery stack111 of n electrochemical cells and an end cathode current collector 60,where n may be equal to 1, from 1 to 2, from 1 to 10, from 1 to 50, from1 to 100, from 1 to 1000, from 1 to 10,000, or from 1 to greater than10,000. The protected-anode multicell battery stack 111 include thecomponents 1 a, 2 a, 3 a, 1 b, 2 b, 3 b, 20 a, 20 b, 30, 40, 60 of thesolid-state battery 100 as previously described with reference to FIG. 3. In addition, the protected-anode multicell battery stack 111 furtherincludes: a first anode protective layer 50 a between the first anode 20a and the first solid-state electrolyte 3 a, and a second anodeprotective layer 50 b between the second anode 20 b and the secondsolid-state electrolyte 3 b. These components will be describedsubsequently in greater detail.

In embodiments, the solid-state electrolyte 3 includes polymer/ceramiccomposite solid electrolyte material, such as a Li₂S—P₂S₅ (LPS) solidconductor, for example, which is selected as the base solid electrolyte.The LPS material has several advantages over LiPON or garnet oxidematerials, including without limitation, intrinsic high ionicconductivity (up to 10⁻² S/cm at 25° C.), potentially low process cost,and good mechanical properties for flexible film forming.

Nonlimiting, example embodiments of methods for preparing an electrodenow will be described. The methods for preparing an electrode mayinclude first compressing an electrode dry mixture to form an electrodefilm of an electrode material. The electrode dry mixture may include anactive material, an electrolyte material, and one or more optionaladditives such as a binder well suited to forming films of the electrodematerial. The methods further include compressing an electrolyte drymixture against a surface of the electrode film to form an electrolytelayer on the surface of the electrode film. The electrolyte dry mixtureincludes electrolyte material and one or more optional additives such asa binder well suited to forming films of the electrolyte material.Compressing the electrode dry mixture may include calendering theelectrode dry mixture. Compressing the electrolyte dry mixture mayinclude first applying the electrolyte dry mixture to the surface of theelectrode film and then calendering the electrolyte dry mixture againstthe surface of the electrode film.

Referring to FIGS. 5A and 5B, from a first dispenser 210, and electrodedry mixture 220 may be compressed between first calender rolls 230 toform an electrode film 240 of the electrode material. Optionally, theelectrode film 240 may be conveyed over one or more additional rollerssuch as side roller 250, depending on the desired manufacturingconfiguration. From a second dispenser 260, dry electrolyte mixture 270then may be applied in powder form directly onto a surface of theelectrode film 240 as it moves toward second calender rolls 280. Theelectrode film 240 serves as a support layer, circumventing the need tohandle very thin free-standing solid-state electrolyte layer. The dryelectrolyte mixture 270 is then compressed against the surface of theelectrode film 240 with force sufficient to provide a solid-stateelectrode film 290, shown in cross-section in FIG. 5B as a solid-stateelectrode 1 including a cathode 2 and a solid-state electrolyte 3. Thesolid-state electrolyte feeding speed, calendering speed, gap, pressure,and temperature may be optimized through a Robust Engineering protocol.Since all the components in the bilayer film is stable up to 320° C.,the electrode film 240 can be heat treated at temperature at 280° C. toimprove its conductivity and strength if necessary.

Thus, when incorporated into a solid-state battery, a cathode 2 isoptionally fabricated using a solvent-free roll mill operation toproduce a free-standing cathode film (such as electrode film 240, forexample). This operation is followed by a second step to apply andlaminate a solid-state electrolyte layer on the cathode. This processproduces a multi-layer stack suitable for high-volume production ofconventional lithium battery architecture and cell formats.

The solid-state electrolyte 3 provided herein may be or may include apolymer/ceramic composite solid electrolyte material based on astructurally modified lithium sulfide. Such a solid-state electrolytedelivers both high Li-ion conductivity and good chemical stability. Asolid-state electrolyte 3 may be formed of a polymer/ceramic compositesolid electrolyte material. A solid-state electrolyte 3 may be formed ofan electrolyte material that is a dry material, a solid material, aceramic material, or a glass-ceramic material. A solid-state electrolyte3 may include a lithium sulfide, a lithium phosphorus sulfide such asxLi₂S-yP₂S₅, or Li₃PS₄ (LPS; xLi₂S-yP₂S₅, where x=75 and y=25). In someaspects a solid-state electrolyte 3 may include a Li₂S—P₂S₅. Thesolid-state electrolyte 3 according to embodiments may be made by ballmilling precursor material(s). Precursor materials are optionallylithium sulfide (Li₂S, 99.98%, Sigma-Aldrich) and phosphoruspentasulfide (P₂S₅, Sigma-Aldrich). Li₂S is optionally provided at 50mol. % to 90 mol. %, or any value or range therebetween. Optionally,Li₂S is provided at 60 mol. % to 80 mol. %, optionally 75 mol. %. P₂S₅is optionally provided at 10 mol. % to 40 mol. %, or any value or rangetherebetween. P₂S₅ is optionally present at 20 mol. % to 30 mol. %,optionally 25 mol. %.

The precursor materials may be intermixed by ball milling usingtechniques recognized in the art. For example, the precursor materialsmay be milled in a zirconia (ZrO₂) jar using a planetary ball mill toform a highly conductive glass electrolyte material such as75Li₂S—25P₂S₅, for example. The glass electrolyte material may beannealed in inert atmosphere such as argon, for example, to increaselithium ion (Li⁺) or ionic conductivity of the glass electrolytematerial.

The resulting electrolyte material may be made into solid-stateelectrolyte 3 by combination with one or more binders, optionally ionconductive polymer binder, optionally fibrillizable binders. An ionconductive binder is optionally PEO. A binder material used in theformation of a solid-state electrolyte optionally includes afibrillizable fluoropolymer, optionally, polytetrafluoroethylene (PTFE).Other possible fibrillizable binders include ultra-high molecular weightpolypropylene, polyethylene, co-polymers, polymer blends and the like.Optionally, a binder material is a combination of any of the foregoing.A binder is optionally combined with the LPS active solid-stateelectrolyte material at a weight ratio of 75:25 to 25:75. Optionally, abinder is present at less than 25 wt. %, optionally less than 20 wt. %,optionally less than 15 wt. %, optionally less than 10 wt. %, optionallyfrom 1 wt. % to 15 wt. %. The LPS and binder powder materials areoptionally dry blended and pressed through a calender machine to a finalthickness.

The solid-state electrolyte 3 has a thickness. A thickness is defined asthe length from one surface to the other from a first side intended tocontact a cathode to a second side substantially opposite the firstside. A thickness is optionally at or less than 100 micrometers (μm).Optionally, a thickness is at or less than 80 μm, optionally at or lessthan 70 μm, optionally at or less than 60 μm, optionally at or less than50 μm, optionally at or less than 40 μm, optionally at or less than 30μm, optionally at or less than 20 μm, optionally at or less than 10 μm.A thickness is optionally 10 μm to 100 μm or any value or rangetherebetween.

A solid-state electrolyte 3 as provided herein has intrinsic high ionicconductivity. Ionic conductivity is optionally up to about 5×10⁻² S/cmwhen measured at 25° C., optionally about 1×10⁻⁴ S/cm to about 5×10⁻²S/cm, optionally about 1×10⁻² S/cm.

In some embodiments, a solid-state electrolyte 3 is optionally formedinto a stand-alone film and then pressed into contact with an electrodeactive material or a cathode 2, for example a free-standing cathode filmas previously described, or is formed into a film layer directly on theelectrode active surface, the cathode 2, or free-standing cathode film,thereby forming a film substantially in situ. Either method may beemployed to produce excellent contact between the solid-stateelectrolyte 3 and the abutting electrode. Thus, methods for forming anelectrode or a solid-state electrode may include compressing anelectrolyte dry mixture, as previously described, to form a stand-alonesolid-state electrolyte film, the electrolyte dry mixture comprising theelectrolyte material, as previously described. The methods may furtherinclude compressing the stand-alone solid-state electrolyte film againsta surface of the electrode film to form a laminate of the electrode filmand the solid-state electrolyte film. Compression of the stand-alonesolid-state electrolyte film against a surface of the electrode film toform the laminate may occur by any suitable method for compressing orlaminating films include, for example, calendering.

A solid-state electrolyte 3 may be contacted with a cathode 2,optionally a cathode active material. A cathode includes at least acathode active material and a current collector such as a cathodecurrent collector 40. The solid-state electrolyte 3 is optionallylaminated to a cathode 2 on a side opposite the cathode currentcollector 40. When using the solid-state electrolyte 3 in a solid statebattery, difficulties arise in obtaining sufficient contact between thesolid-state electrolyte 3 and the cathode 2. To solve this problem, theinventors have found that intermixing the cathode active material with asolid Li ion conductor, optionally LPS, LiNbO₃ or combinations thereof,improves this connection for improved ionic conductivity. Thereby, inthe formation of a cathode 2, a cathode active material powder isoptionally intermixed with or coated with LPS. Such intermixing showssignificantly improved results, particularly when used with cathodesthat are formed by dry processes such as those described inWO/2017/197299.

The solid-state electrolyte 3 can be used with many electrochemicallyactive cathode active materials. Illustrative active electrode materialsinclude nickel manganese cobalt (NMC622, NMC811, NMC532) (a.k.a. NCM orNMC), lithium manganese spinel (LMO), lithium nickel manganese spinel(LNMO), lithium nickel cobalt aluminum oxide (NCA), lithium ironphosphate (LFP), lithium iron manganese phosphate (LmFP), lithium cobaltoxide (LCO), and graphite formulas, or combinations thereof. Inparticular examples, an electrochemically active material is one or moreNCM or LCO materials, optionally at the exclusion of one or more otherelectrochemically active materials.

In embodiments, an electrode active material is optionally coated orcompounded with a solid Li-ion conductor such as LPS, for example, suchthat the electrode film is a composite of the electrolyte material andthe active material. The electrolyte material of the cathode 2 may bethe same as or different from the electrolyte material in thesolid-state electrolyte 3. Coating is optionally on a powder formelectrode active material prior to combination with a binder or coatingor otherwise contacting a current collector substrate. Powder electrodeactive material may be combined with LPS powder (for example) where theelectrode active material is present as a predominant. The materials maybe premixed such that the electrode active material is coated with theLPS. The premixed material may then be combined with a binder,optionally a fibrillizable binder, to form the final cathode activematerial according to some aspects.

Referring to FIG. 6 , an example coating process 300 for electrodeactive material is provided, leading to formation of an electrodematerial that subsequently may be compressed to form a cathode 2. In theexample coating process 300, an electrode dry mixture 310 may beprepared by combining active material particles 312 and electrolytematerial particles 314. The combined particles may then be processed ina step 315 by mixing, agitation, or milling, with or without heat, toform a composite 320 of the active material particles 312 coated with orsubstantially surrounded by the electrolyte material particles 314. In astep 325, optional additives such as binder or carbon may be added tothe composite 320, and the resulting mixture 330 (shown in schematic)may be further mixed or processed, with or without heat, in preparationfor compressing step 335. The compressing step 335 forms the cathode 2as a composite film including regions of active material 340 within amatrix 345 including the electrolyte material and any optional additivessuch as binders or conductors such as carbon. The cathode 2 as thecomposite is thus suitable for transport of lithium ions 350 from oneside of the cathode 2 to the opposite side of the cathode 2.

Binders such as polytetrafluoroethylene (PTFE) or polyvinylidenefluoride (PVdF) powders may be blended into the coated active materialsand fibrillized under high-shear mixing. After fibrillization, theelectrode materials can be processed into a free-standing film byfeeding into a roll mill. The free-standing films may be laminated tometal foil current collectors, perhaps following additional passesthrough the roll mill to attain the desired electrode film thickness andporosity. An electrode film thickness may be from about 30 μm to about500 μm, optionally about 50 μm to about 200 μm, optionally about 100 μmor more, optionally about 50 μm or more.

In embodiments, the composite cathode powder including the activematerial is blended with carbon and dry PTFE binder powder with astarting formulation of “active/carbon/PTFE=82/10/8”. The blend may becalendered to form a free-standing film at a suitable speed, such as 0.5meter/min, and at a suitable pressure, such as 3000 psi.

The cathode film may be laminated to aluminum foil to form a cathodethrough the calender machine.

According to embodiments, the solid-state electrolyte powder and PTFEbinder powders may be blended with a binder content of 5 wt. % to 10 wt.%. In embodiments, the composite cathode films may be formed bycompressing the blend using a hydraulic press at a pressure such as 360MPa. The composite cathode film can also be prepared by passing theblend through a jeweler mill at a pressure of from 1000 psi to 3000 psi.

In embodiments of the methods for preparing an electrode such as asolid-state electrode 1, the electrolyte material of the electrolyte drymixture, the electrode dry mixture, or both, may include an additive ordopant, such as an air-stabilizing dopant, that stabilizes theelectrolyte materials such as Li₂S—P₂S₅ and prevents degradation of thematerials in air. Materials such as Li₂S—P₂S₅ often have low stabilityin air and must be handled in inert atmosphere during processing steps.

Air-stabilizing dopants that may improve the chemical stability of thesulfide electrolytes such as LPS in moist air, may be chosen based onthe following principles: (1) The additive should have stronger waterabsorption ability than that of Li₂S so that reaction between sulfidesand moisture in the air can be suppressed; (2) The additive shouldsuppress the formation of H₂S; (3) The Li₂S—P₂S₅ even with small amountof additives should still maintain a high ionic conductivity; (4) Theadditive should be stable with Li metal to achieve a long-term cyclingstability; and (5) The additive should be an electronic insulator toreduce the self-discharge rate.

An example air-stabilizing dopant may include ZnO as an additive tostabilize lithium sulfides such as 75Li₂S·25P₂S₅. Further examples ofair-stabilizing dopants include CaO and ZrS₂. Both CaO and ZrS₂ areinert to Li metal. CaO has stronger capability for absorbing themoisture than ZnO and also has larger negative Gibbs energy change (AG)for the reaction with H₂S in improving the sulfide stability. ZrS₂ isintrinsically stable in water and air.

Doped, air-stabilized sulfide powder, Li₂S and P₂S₅ (75/25) may besynthesized by ball-milling at 500 rpm for 10 hours (Retsch PM-100Planetary Mill). The solid electrolyte powder may be mixed with from 0to 10 wt. % ZnO, ZrS₂, or CaO dopant by a second ball milling process.

A cathode is optionally formed by adding an engineered porosity carbonmaterial as a processing additive along with activated carbon or inplace of activated carbon with a fibrillizable binder material in a dryprocess cathode manufacturing method. Optionally, a processing additiveis not activated carbon. A processing additive optionally has a surfaceroughness on a dimensional scale that is within 10% to 250% of thatfound in PTFE fibers. Such a surface is rough on a dimensional scalewhere roughness is defined as a plurality of hills and valleys on thesurface of the processing additive. In some aspects of the disclosure, asurface roughness defines a porous surface structure, optionally asurface structure having high porosity. High porosity is defined as apore diameter of about 10 nm to about 1000 nm having a cumulative porevolume of about 0.8 mL/g to about 2.5 mL/g, or having a porous structurewith a density of about 1500 kg/m³ to about 2500 kg/m³. Optionally, thecumulative pore volume is about 1.0 mL/g to about 2.5 mL/g, optionallyabout 1.2 mL/g to about 2.2 mL/g, optionally with a pore diameter ofabout 10 nm to about 1000 nm. In some aspects, the processing additivehas a cumulative pore volume of optionally of or greater than 0.8 mL/g,optionally about 0.9 mL/g, 1.0 mL/g, 1.1 mL/g, 1.2 mL/g, 1.3 mL/g, 1.4mL/g, 1.5 mL/g, 1.6 mL/g, 1.7 mL/g, optionally 1.8 mL/g, 1.9 mL/g, 2.0mL/g, 2.1 mL/g, 2.2 mL/g, 2.3 mL/g, 2.4 mL/g, 2.5 mL/g. For comparison,activated carbon has a pore volume of about 0.9 mL/g. The processingadditive for example, without limitation, may have a porosity of about30 vol. % to about 40 vol. %, or any value or range therebetween,optionally about 35 vol. % to about 40 vol. %, optionally about 30 vol.%, 31 vol. %, 32 vol. %, 33 vol. %, 34 vol. %, 35 vol. %, 36 vol. %, 37vol. %, 38 vol. %, 39 vol. %, 40 vol. %.

Examples of a processing additive as used herein include carbonmaterials. Examples of carbon materials include graphitized carbon andactivated carbon. Further examples of carbon materials include asilica-templated high-porosity optionally graphitized carbon material.Example carbon materials may have a particle size distributionoptionally peaking in about the 3 micrometer (μm) to about 5 μm range.In some aspects, the BET area of the carbon material may be much lessthan that of conventional AC. In some embodiments, the carbon materialis not activated and thus is less hydrophilic than AC. Thegraphitization process imparts mechanical strength comparable to thepyrolized highly-cross linked cellulosic precursor sources used to formAC. An illustrative example of a processing additive such as porouscarbon is sold as POROCARB by Heraeus Quarzglas GmbH & Co. KG,Kleinostheim, Germany.

A manufacturing method for exemplary porous carbon particles for use asa processing additive herein may be found in U.S. Pat. No. 9,174,878. Ingeneral, a porous metal oxide template of agglomerated or aggregatedmetal oxide nanoparticles is first produced by hydrolysis or pyrolysisof a starting compound by means of a soot deposition process. The poresare infiltrated with a carbon precursor substance. After carbonization,the template is again removed by etching. What remains is a porouscarbon product having a hierarchical pore structure with platelet-likeor flake-like morphology.

In some aspects of the disclosure, a processing additive is a hardcarbon with mechanical properties similar to activated carbon withregard to properties such as particle strength, particle morphology, orsurface roughness, which may contribute to the electrode processibility,but with lower porosity, lower surface area (e.g., as measured by gasadsorption), or less hydroscopic than activated carbon. An illustrativeexample of a hard carbon is sold as LBV-1 Hard Carbon from SumitomoBakelite Co., LTD. Such a material may be obtained from pyrolizinghighly cross-linked cellulosic precursors. Whereas commercial ‘activatedcarbon’ materials are subjected to a pore-forming activation processprior to particle size reduction and classification, the desiredexemplary processing additive may be formed by excluding the activationprocess. The exemplary processing additive optionally has a BET surfacearea less than 200 m²/g and preferably less than 20 m²/g, compared toareas greater than 800 m²/g for commercial activated carbon.

A processing additive has a particle diameter. It is preferred thatparticle diameters of 50 μm or less are used. Optionally, a processingadditive has an average particle diameter of 1 μm to 50 μm, optionally 1μm to 30 μm, optionally 1 μm to 25 μm, optionally 1 μm to 20 μm,optionally 1 μm to 5 μm, optionally 3 μm to 10 μm.

A processing additive is optionally present at an amount such as 20% to75% the amount of binder used to form the electrode. Optionally, theprocessing additive is present at a 30% to 60%, optionally, 40% to 70%,optionally 50% to 70%, the amount of binder. In some aspects of thedisclosure, the processing additive is used to the exclusion ofactivated carbon. Optionally, the processing additive replaces someamount of activated carbon, but the processing additive and theactivated carbon are used together.

A processing additive is optionally included at an amount relative to anoverall weight of the electrode material. An overall amount ofprocessing additive is optionally from 2 wt. % to 10 wt. %, optionallyfrom 2 wt. % to 6 wt. %, optionally from 4 wt. % to 8 wt. %, optionallyat 5 wt. %, based on the total weight of the electrode material. In someaspects of the disclosure, the overall concentration of processingadditive is optionally greater than or equal to 5 wt. %, optionally 5wt. % to 8 wt. % or greater than 8 wt. %, optionally when blended withan active material such as LFP, NMC, LmFP, or the like.

In some aspects, an electrode includes a conductive carbon. Theconductive carbon as used herein may be an activated carbon (AC) as isotherwise described herein. The dispersed conductive carbon network maybe described in some cases as “chain of pearls.” In other casesconductive carbons may be high aspect ratio fibers or platelets that canwrap powders and/or form a web type network. In some aspects, electrodesmay use combinations of conductive carbons. On the other hand, activatedcarbon generally refers to very high surface area microporous materials.Conductive carbons may or may not be porous but in many cases are alsohigh surface area but with more of the surface area due to exterior ofsmall particles rather than internal pore volume as is the case foractivated carbons. Commercial activated carbons are generally muchlarger particles than conductive carbons.

The inventors discovered that mere combining of a processing additivewith a LPS intermixed with active material and a binder resulted in poordry process electrode active material. However, by dispersing theprocessing additive in the active electrode material or thefibrillizable binder and subsequently intermixing the previously omittedcoated active electrode material or the fibrillizable binder improvedthe processing characteristics and electrochemical properties of theresulting electrodes. Thus, the combination of elements of a resultingfilm may require particular order and dispersion properties, withoutwhich the intermixing of the processing additive with the entire set ofmaterials was non-optimal. In embodiments, the electrode material may beprocessed by first intermixing the processing additive with either thebinder or the coated active material prior to combination with theother.

The electrode active material (active, LPS, binder, optional carbon,optional processing additive) is formed prior to coating onto a currentcollector. A current collector is optionally a metal foil. A metal foilcurrent collector may be an aluminum foil, a copper foil or optionallyanother conductive metal foil. In some aspects, the electrode activematerial is a free flowing powder prior to coating onto a currentcollector. Optionally, an electrode active material is formed into afree standing film then laminated to a current collector. In someaspects, the electrode precursor materials herein contain no more wateror other liquid solvent than the ambient atmosphere, optionally lessthan 1% of any liquid including for example solvents, water, ethanol, orthe like. The improved processibility of the materials formed using theprocessing additive and by methods as described herein is furtherenhanced by the dry aspects of the materials that provide more rapidoverall electrode manufacture.

The electrode dry mixture or electrode precursor material may besubsequently passed through a 355-micron sieve before formation into afree-standing film. Once the electrode precursor material is formed, theelectrode precursor material is fed into a roll mill and calendered toform a free-standing film. The free-standing film may be formed bycalendering the free flowing electrode precursor material at a rolltemperature and roll speed under a hydraulic pressure. The rolltemperature may be from about room temperature (20° C.) to about 180° C.A higher the roll temperature may result in a thinner free-standing filmon the first pass compared to a lower temperature. Additionally, theroll speed may be set from about 0.17 m/min to about 1.3 m/min. A slowerroll speed may result in a thinner free-standing film on the first passcompared to a faster roll speed. A hydraulic pressure of about 1,000 psito about 7,000 psi may be used. A higher pressure may result in athinner free-standing film on the first pass compared to a lowerpressure. Additional passes through the roll mill may continue to reducethe film thickness until desired thickness and loading are obtained. Insome aspects of the disclosure, an example, without limitation, filmthickness may be about 50 μm to about 150 μm, optionally about 50 μm, toabout 100 μm, optionally about 100 μm to about 150 μm, optionally about50 μm, about 55 μm, about 65 μm, about 70 μm, about 75 μm, about 80 μm,about 85 μm, about 90 μm, about 95 μm, about 100 μm, about 105 μm, about110 μm, about 115 μm, about 120 μm, about 125 μm, about 130 μm, about135 μm, about 140 μm, about 145 μm, or about 150 μm. In some aspects ofthe disclosure, an example, without limitation, desired loading may beabout 19 mg/cm² to about 21 mg/cm², optionally about 19 mg/cm²,optionally about 20 mg/cm², or optionally about 21 mg/cm².

The free-standing film may be laminated on a substrate such as a metalfoil current collector to form an electrode. Lamination may occur byrolling the free-standing film together with the metal foil currentcollector at a roll temperature and roll speed under a hydraulicpressure. The roll temperature is preferably about 100° C., oroptionally 80° C. or 90° C. It is appreciated that the higher the rolltemperature the greater the likelihood of blistering and poor adhesion.Similarly, the lower the roll temperature, the worse the adhesion.Additionally, the roll speed may be from about 0.17 m/min to about 1.3m/min, optionally about 0.5 m/min. Finally, the hydraulic pressure maybe set from about 500 psi to about 2,000 psi. The pressure is set topromote adhesion to the substrate but not such that the chemicalproperties, for example loading and porosity, are altered. When thepressure is set too high, the chemical properties are affected, but whenthe pressure is set too low adhesion may not occur.

The processes and electrode films produced thereby achieve a drymanufacture method that creates excellent electrochemical properties toresulting electrodes suitable for use in lithium ion or other cells.

The solid-state electrode 1 prepared as described herein may be furtherprocessed to form multilayer functional structures such aselectrochemical cells and solid-state batteries. Accordingly,embodiments include electrochemical cells or batteries having at leastone solid-state electrode 1 as previously described. As previouslydescribed, a cathode 2 may be laminated to a solid-state electrolyte 3as provided herein. Optionally, a stand-alone solid-state electrolyte 3film may be laminated onto the cathode 2 to form a cathode/SSE bi-layercoupon by controlling the calender roll gap, pressure, and speed. Theresulting bilayer structure uses the cathode as a mechanical support andenables a thin SSE film on top to be strong and flexible.

The cathode/SSE bi-layer or solid-state electrode 1 may be furtherprocessed to form additional layer structures. For example, referring toFIG. 7 , in an example lamination process 400, separate layers such as acathode current collector 40, a first solid-state electrode 1 a, a firstanode 20 a, an anode current collector 30, a second anode 20 b, and asecond solid-state electrode 1 b, may be laminated together. Thelamination of the layers may occur after first physically stacking thelayers, then compressing the layers such as by passing the layersthrough a calendering roll 410. The lamination process may occur inmultiple steps, such as one layer at a time, or in fewer steps, by whichmultiple layers may be laminated in a single pass. The lamination stepsresult in a structure such as the solid-state battery 100 having amulticell battery stack 110, as previously described. Multiple processrepetitions may occur to increase the number of cells (n) in themulticell battery stack 110.

A cathode film serves as the substrate for fabricating the SSE layer ina sequential roll mill operation. In the second dry process step, thesame sulfide is applied, consolidated and laminated to the cathode. Thisapproach may impart a continuous and low impedance interface to thecathode. In such processes, there is no need to handle free-standingcathode or need for subsequent application of heat or pressure. Thepolymer content, although low, may provide the flexibility needed toaccommodate strain mismatches between the cathode and the anodeassociated with lithiation/delithiation and/or thermal expansion.

In embodiments, the bilayer film or solid-state electrode 1 can belaminated to a suitable counter electrode, optionally Li foil, to form amulti-layer stack which is suitable for high volume production of asolid-state battery. The resulting cathodes and solid-state electrolytesmay be used in any suitable solid state battery configuration.Illustrative configurations include coin cells, pouch cells, or othercell configuration as known in the art.

In some embodiments, the bilayer film or solid-state electrode 1 may belaminated to a counter electrode such as an anode 20 including an anodeprotective layer 50. The anode 20 may include Li foil, for example. Theanode protective layer 50 may be a substance such as a ceramic thatprevents degradation of the anode 20 or that reduces interfacialstresses between the anode 20 and a solid-state electrolyte 3 of thesolid-state electrode 1 laminated to the anode 20. Non-limiting examplesof materials suitable as the anode protective layer 50 may includeLiPON. The anode protective layer 50 may have any thickness thataccomplishes the purpose of protecting the anode 20 withoutsubstantially degrading current flow or ion transport across thesolid-state electrolyte 3. The anode protective layer 50 may have athickness of up to 0.1%, up to 0.5%, up to 1%, up to 2%, up to 5%, up to10%, up to 20%, up to 30%, or up to 40% the thickness of the anode 20.Example lamination processes are described with reference to FIGS. 8 and9 .

Referring to FIG. 8 , in a first example lamination process 500, ananode protective layer 50 is applied to a surface of an anode 20 to forma bilayer 510. The anode protective layer 50 may be applied to thesurface by any deposition method such as physical vapor deposition,chemical vapor deposition, or sputtering, for example. The bilayer 510is then laminated to a solid-state electrode 1 according to embodimentsof this disclosure to form a cell 520. The lamination is conducted withthe anode protective layer 50 of the bilayer 510 facing the solid-stateelectrolyte 3 of the solid-state electrode 1. The lamination may beaccomplished by any technique suited for joining films such as, forexample, passing the bilayer 510 and the solid-state electrode 1 throughcalendering rolls.

Referring to FIG. 9 , in a second example lamination process 600, ananode protective layer 50 is applied to a surface of a solid-stateelectrode 1 according to embodiments of this disclosure and including acathode 2 and a solid-state electrolyte 3 to form a trilayer 610. Theanode protective layer 50 may be applied to the surface by anydeposition method such as physical vapor deposition, chemical vapordeposition, or sputtering, for example. The trilayer 610 is thenlaminated to an anode 20 to form a cell 620. The lamination is conductedwith the anode protective layer of the trilayer 610 facing the anode 20.The lamination may be accomplished by any technique suited for joiningfilms such as, for example, passing the trilayer 610 and the anode 20through calendering rolls.

Various aspects of the present disclosure are illustrated by thefollowing non-limiting examples. The examples are for illustrativepurposes and are not a limitation on any practice of the presentdisclosure. It will be understood that variations and modifications canbe made without departing from the spirit and scope of the disclosure.Reagents and materials illustrated herein are obtained from commercialsources unless otherwise indicated.

EXAMPLES Example 1 Solid-State Electrode Fabrication

For formation of an exemplary SSE, 75Li₂S-25P₂S₅ solid electrolyte wasprepared by a mechanical milling method. A mixture of 75 mol. % oflithium sulfide (Li₂S, 99.98%, Sigma-Aldrich) and 25 mol. % ofphosphorus pentasulfide (P₂S₅, Sigma-Aldrich) was milled in a zirconia(ZrO₂) jar using a planetary ball mill. A highly conductive75Li₂S-25P₂S₅ glass electrolyte powder was formed. The obtained LPSglass electrolyte powder was annealed in Ar at 270° C. to form a LPSglass-ceramic electrolyte having greater conductivity than the LPS glasselectrolyte powder.

X-ray diffraction (XRD) was performed on the LPS glass electrolytepowder and the LPS glass electrolyte powder using a Bruker D8 ADVANCEXRD. XRD patterns of a LPS-glass and a glass-ceramic electrolyte areshown in FIG. 10 . There is no sharp peak in the pattern of the glasselectrolyte, indicating non-crystalline structure of as-preparedLPS-glass. The broad peaks from 10° to 40° are from the polymeric sampleholder (background). After the 270° C. annealing, some sharp peaksappear in the XRD of the LPS glass-ceramic material, indicating theexistence of crystalline structure. Without intent to be bound bytheory, it is believed that the crystalline structure may enhance theconductivity of the electrolyte, but with possible trade-off ofdesirable mechanical properties.

Raman spectra of the LPS glass-ceramic powder were collected on a HoribaARAMIS Raman. The Raman spectra confirmed the Li₃PS₄ structure of thematerial, which contributes to a high ionic conductivity in thisexample. Referring to FIG. 11 , Raman spectra of the LPS glass-ceramicelectrolyte confirmed the presence of PS₄ ³⁻ groups in the electrolyte.

Ionic conductivity of the LPS glass material and the LPS glass-ceramicmaterial SSE material were measured from a Pt/LPS/Pt cell usingelectrochemical impedance spectroscopy (EIS). The powders were coldpressed to form pellets with 1 mm thickness and 10 mm diameter. Anion-blocking Pt/Li₃PS₄/Pt cell was then prepared by sputtering theelectrolyte pellet with platinum. AC impedance of the cells weremeasured from 10⁵-10⁻² Hz via a Solartron Impedance Analyzer. From theimpedance plot of FIG. 12 , ionic conductivity of the LPS glass materialwas calculated to be 3.2×10⁻⁴ S/cm and the ionic conductivity of the LPSglass-ceramic material was calculated to be 1.3×10⁻³ S/cm.

Cyclic voltammetry (CV) was performed on the LPS glass-ceramic materialto evaluate its electrochemical stability. The electrolyte powder wascold pressed to form a pellet with 1 mm thickness and 10 mm diameter.Platinum was sputter coated on one side of the pellet. The coated pelletwas then assembled into a cell with Li metal as counter/referenceelectrode. The Pt/LPS/Li cell was scanned from −0.5 V to +5 V vs. Li/Li⁺at a rate of 0.1 mV/s. Referring to FIG. 13 , CV plot indicates theelectrolyte intrinsic stability from 0 to +5 V on a non-active surface.

Lab scale solid state cells were assembled and evaluated for rateperformance. The cells included the LPS as a solid state electrolyte,LiCoO₂ (LCO) as a cathode, and a Li metal foil as an anode.

The major difference between the SSB composite cathode and a standard Liion cathode is that the composite cathode needs a solid Li-ion conductorin its structure for ionic conductivity. LCO active powder was premixedwith LPS electrolyte powder in a weight ratio of 7:3. The mixture wasthen dry blended with carbon additive and PTFE binder. The dry blend wascalendered to form a cathode film. A stand-alone cathode film wasfabricated.

The stand-alone cathode film then was laminated to Al foil to form thecathode through the calender machine. The composite cathode loading was3.0 mAh/cm² and its dimensions were 53 mm×94 mm.

Similar to the cathode film fabrication, formation of the SSE layer wasachieved by dry blending the LPS powder with PTFE binder in a weightratio of 1:1. Other examples use a LPS powder with PTFE binder in aweight ratio of 9:1. A stand-alone electrolyte film was formed bycompressing 120 mg of the dry blend through a calender machine to form a10 mm diameter LPS membrane. The film thickness was controlled to be 100μm.

The stand-alone SSE film was laminated onto the cathode under 3 MPapressure to form a cathode/SSE bi-layer coupon by controlling thecalender roll gap, pressure, and speed. Subsequent studies formed astack with dimensions over 60 mm×100 mm that meets the size requirementof a test pouch cell. Test cells were formed by combining thecathode/SSE bilayer with a Li anode. Two stainless steel rods were usedas current collectors. The cells rested for 10 h prior to testing. Thecell current density was controlled at ≤0.25 mA/cm² to avoid non-uniformLi volume change and Li dendrite growth.

Galvanostatic charge/discharge cycles were conducted using a batterycycler (LAND CT-2001A) from 2.7 V to 4.2 V at room temperature. Thecurrent density and specific capacity were calculated based on theweight of the LCO.

For discharge rate capability testing, the cell was charged at C/10 rateand discharged at various rates (i.e., C/10, C/5, and C/2). Referring toFIG. 14 , the cell exhibited 90% capacity retention at C/5 rate and 75%at C/2 rate, when compared to the initial capacity at C/10. Theseresults confirm the capability of the solid cell to handle operation ina commercial battery.

The LCO shows a reversible capacity of 110 mAh/g in the solid cell,which is comparable to that in a conventional liquid electrolyte cell.An initial capacity loss (ICL) ranging from 18% to 30% was observed onthe solid cells due to formation of passivation layers between the SSEand the electrodes. Cycle life of the cell was tested over 2.7 V-4.2 Vat C/5 and at room temperature. The cell capacity and efficiency areshown in FIG. 15 . The capacity retention vs. cycle number is shown inFIG. 16 . The cell was cycled for 120 cycles with 85% capacityretention. The cycling efficiency stabilized at >99.5%. A cycle life of250 is projected from the cell cycling trend.

Example 2 Fabrication of Pouch Cell Including Solid-State Electrolyte

As a further example, 250 mAh pouch cells were fabricated. For thecathode and SSE fabrications, 100 grams of SSE powder was required. ARetsch Planetary Ball Mill PM200 and two 125 mL jars were used toproduce the SSE powder. Non-coated LCO powder was used as the cathodematerial. Without a metal oxide buffering layer, the space-charge layerbetween LCO and LPS introduces a significant increase of interfacialresistance. Under the same condition, the bare LCO cathode shows 45%lower capacity than the S-LCO (LiNbO₃ modified) capacity in solid cells(i.e., 60 mAh/g vs. 110 mAh/g). The bare LCO also shows higherpolarization than the S-LCO. The voltage profiles of the two cathodesare shown in FIG. 17 for comparison.

A major difference between the SSB composite cathode and a standard Liion cathode is that the composite cathode needs a solid Li ion conductorin its structure for ionic conductivity. LCO active powder was premixedwith LPS electrolyte powder with ratio of 7:3. The mixture was then dryblended with carbon additive and PTFE binder. The dry blend wascalendered to form a cathode film. With parameter investigationincluding calender gap, speed, and pressure, a stand-alone cathode filmwas fabricated.

The stand-alone cathode film was then laminated to Al foil to form thecathode through the calender machine. The composite cathode loading isdesigned to be 3.0 mAh/cm² and its dimension is 53 mm×94 mm.

Similar to the cathode film fabrication, the LPS powder was dry-blendedwith PTFE binder with a weight ratio of 1:1. A stand-alone electrolytefilm was formed by compressing the dry blend through a calender machine.The film thickness was controlled to be 100 μm. The stand-alone SSE filmwas laminated onto the cathode to form a cathode/SSE bi-layer coupon bycontrolling the calender roll gap, pressure, and speed.

After forming the cathode/electrolyte bi-layer film, a Li metal anodewas laminated to the bi-layer coupon to form “Li-SSE-Cathode” tri-layerstack having dimensions of over 60 mm×100 mm. All the processes,including electrode fabrication, electrolyte fabrication, and tri-layerstack lamination, were determined to be readily scalable to aroll-to-roll operation.

A double-layer-pouch (DLP) cell was fabricated by laminating adouble-sided LCO cathode between two electrolyte films laminated to eachside. Two single-sided Li-metal anodes (on Cu foil) then were laminatedto the cathode/electrolyte coupon to form a stack having layersCu—Li/LPS/LCO-Al-LCO/LPS/Li—Cu. The current collector was ultrasonicallywelded to a heat sealable tab. This stack was heat sealed into analuminum laminate pouch cell packaging to produce the DLP cell.

Example 3 Air-Stabilized Doped Electrolyte

An air-stable, doped electrolyte was prepared for use as the SSEmaterial in electrochemical cells. The electrolyte from a mixture of 90wt. % 75Li₂S-25P₂S₅ and 10 wt. % ZnO milled in a zirconia (ZrO₂) jarusing a planetary ball mill. A highly conductive doped electrolytepowder was formed. The obtained doped electrolyte powder was annealed inAr at 270° C. to form a doped glass-ceramic electrolyte powder havinggreater conductivity than the doped glass electrolyte powder.

Ionic conductivity was measured on the doped glass-ceramic electrolytepowder at various time intervals after being exposed to air in a dryroom, from an initial measurement after annealing to 12 hours afterannealing. As shown in FIG. 18 , the doped glass-ceramic electrolyteexhibited no appreciable change to its ionic conductivity after 12hours. The tested sample had an initial Li⁺ conductivity of less than10⁻⁴ S/cm.

The maximum conductivity of liquid electrolytes, such as ethylenecarbonate/dimethyl carbonate with 1-M LiPF₆, is on the order of 10⁻²S/cm at 25° C., and the transport number of lithium ions is in the rangeof 0.2 to 0.5. Ionic conductivity on the order of 10⁻³ S/cm at 25° C. isdesirable for solid state electrolytes to deliver performances similarto that of liquid electrolytes, considering that the transport number insolid state electrolyte is 1.0. The SSE films according to embodimentsof this disclosure have been demonstrated to have sufficient ionicconductivity to bring the SSB power density up to that of commerciallithium-ion batteries with liquid electrolytes.

As electrode loadings are increased to meet energy density goals, theSSB capacity retention at higher rate may be limited by chargetransport. A commercial battery typically operates at a rate less thanor equal to C/2. Electrochemical cells and batteries including the SSEaccording to embodiments of this disclosure have improved conductivityto enable capacity retention at high loading. The solid state batteriesaccording to embodiments further may include a stackable unit layer, ascalable cell form, a flexible cell design, and the ability to meet andcontrol interfacial impedance over meaningful area or dimension. Thesolid state batteries may meet energy density requirements of greaterthan 250 Wh/kg and greater than 600 Wh/l with the unit stack.

The electrochemical cells and SSBs according to embodiment of thisdisclosure may have comparable cycle life to those of advancedhigh-energy Li-ion cells and at least double the cycle life of the highenergy all-solid-state cells. Cycle life has been a key barrier to thecommercialization of high energy all-solid-state batteries although lowenergy thin film SSB's achieve thousands of cycles. The cycle lifelimitation is ascribed to two root causes. One is poor electrochemicalstability between electrolyte and electrodes, which results in theincremental resistance rise with cycling at the SSE/active interface.The second cause is the incompatible dimension changes betweenelectrolyte and active materials, which also results in the incrementalinterfacial resistance increasing with cycling. The SSEs and SSBsaccording to embodiment may address both causes. The SSE film leads toboth high density and elasticity, allowing a good contact betweenelectrolyte and active materials through repeatedlithiation/delithiation cycles.

Various modifications of the present disclosure, in addition to thoseshown and described herein, will be apparent to those skilled in the artof the above description. Such modifications are also intended to fallwithin the scope of the appended claims.

It should be appreciated that all reagents are obtainable by sourcesknown in the art unless otherwise specified.

Patents, publications, and applications mentioned in the specificationare indicative of the levels of those skilled in the art to which thedisclosure pertains. These patents, publications, and applications areincorporated herein by reference to the same extent as if eachindividual patent, publication, or application was specifically andindividually incorporated herein by reference.

The foregoing description illustrates particular aspects of thedisclosure but is not meant to be a limitation upon the practicethereof.

What is claimed is:
 1. An electrode comprising an electrode dry mixtureand a dry electrolyte material intermixed with the electrode drymixture; and a binder intermixed with said electrode dry mixture andsaid dry electrolyte material, said binder in the form of fibrils;wherein the electrode dry mixture comprises an active material, andwherein said dry electrolyte material comprises from 0.1% to 15% byweight air-stabilizing dopant, based on the total weight of the dryelectrolyte material.
 2. The electrode of claim 1, wherein the activematerial comprises nickel manganese cobalt, lithium manganese spinel,lithium nickel manganese spinel, lithium nickel cobalt aluminum oxide,lithium iron phosphate, lithium iron manganese phosphate, lithium cobaltoxide, graphite, or combinations thereof; and the dry electrolytematerial comprises a lithium phosphorus sulfide glass ceramic.
 3. Theelectrode of claim 1, wherein the dry electrolyte material comprises aglass ceramic.
 4. The electrode of claim 1, wherein the dry electrolytematerial comprises a lithium phosphorous sulfide glass ceramic.
 5. Theelectrode of claim 1, wherein the dry electrolyte material comprisesLi₃PS₄ glass ceramic.
 6. The electrode of claim 1, wherein theair-stabilizing dopant is selected from the group consisting of ZnO,CaO, ZrS₂, and combinations thereof.
 7. The electrode of claim 1,wherein the active material comprises nickel manganese cobalt, lithiummanganese spinel, lithium nickel manganese spinel, lithium nickel cobaltaluminum oxide, lithium iron phosphate, lithium iron manganesephosphate, lithium cobalt oxide, graphite, or combinations thereof. 8.The electrode of claim 1, wherein the electrode further comprises asecond electrolyte dry mixture compressed against a surface of theelectrode to form an electrolyte layer on the surface of the electrodefilm, the second electrolyte dry mixture comprising the dry electrolytematerial.
 9. The electrode of claim 8, wherein the second electrolytedry mixture further comprises an electrolyte binder chosen fromfibrillizable polymers, polytetrafluoroethylene, and poly(vinylidenefluoride), ultra-high molecular weight polypropylene, polyethylene, andcopolymers or blends thereof.
 10. The electrode of claim 1, wherein: theactive material comprises lithium cobalt oxide or nickel manganesecobalt; the dry electrolyte material comprises Li₃PS₄ glass ceramic; andthe binder comprises a fibrillizable polymer binder chosen frompolytetrafluoroethylene, and poly(vinylidene fluoride), ultra-highmolecular weight polypropylene, ultra-high molecular weightpolyethylene, and copolymers or blends thereof.
 11. The electrode ofclaim 1, wherein the electrode further comprises a stand-alonesolid-state electrolyte film laminated against a surface of theelectrode film; wherein the stand-alone solid state electrolyte filmcomprises the dry electrolyte material.
 12. The electrode of claim 1,wherein said binder is present at 10 percent by weight or less of thetotal of said electrode dry mixture, said dry electrolyte material, andsaid binder combined.
 13. An electrochemical cell comprising theelectrode of claim
 1. 14. The electrochemical cell of claim 13 whereinthe dry electrolyte material comprises a lithium phosphorus sulfideglass ceramic.
 15. The electrochemical cell of claim 13 comprising ananode layer, wherein the anode layer is a Li foil protected on at leastone surface with an anode protective layer, the anode protective layercomprising LiPON.